Preparation of zincate solutions.



. G. HANSON.

PREPARATION OF ZINGATE SOLUTIONS.

APPLICATION FILED JULY 8, 1910.

1,023,964. 7 Patented Apr. 23, 1912.

CHARLES reason, or rears, raancnj rnnrenarron or ZINCATE soilurrons,

Specification of Letters Patent.

Patented Apr. eaters.

Application filed Jul s, 1910, Serial No. 570,956.

7 '0 all whom, it may concern:

Be it known that I, CHARLES HANSON, of 2 Rue Poncelet, Parls, France, have invented certain new and useful Improvements in the-Preparation of Zincate Solulutions, of which the tollowingis a specification. p

This invention relates to the preparation from zinc oxid ores or from roasted zinc '1 blendes, of pure solutions of zincates suitable for instance for the manufacture of caustic alkalis and zinc sulfid pigments. According to the process described in U. S. Patent No. 818,192 granted to me in 1906 I prepare such solutions by the action of caustic alkalis or alkaline earths on metallic zinc, when hydrogen gas is obtained as a by-product. Where the latter by-product possesses little or no commercialvalue and zinc ores are readily available it is however more economical to prepare the zincate solutions from the ores direct, it necessary after they have been previously calcined in the known Way to convert the ore into 25, oxid of zinc. For example ores containing blende (sulfid of zinc) may be heated to a high temperature in contact with air. The zinc sulfid is thus oxidized, giving oxid of zinc and sulturous anhydrid. Ores containing calamin (carbonate of zinc) will be calcined at the temperature of incipient red heat, the carbon dioxid is evolved'and the oxid of zinc liberated. I have however found that by digestion of the zinc ore with solutions of caustic alkalis or alkaline earths, although zinc oxid is dissolved out in the form of zincate, the extraction is either imperfect and the degree of concentration too low for practical purposes, or the solu- 40 tions are contaminated to such an extent by silica and other impurities likewise dissolved from the ore, that they are unsuitable for the uses contemplated.

I have now discovered a method whereby .15 relatively very pure and concentrated solutions of zincates or zinc oxid in caustic alkalis can be prepared from ores, without the caustic alkali coming into direct contact with the ore. monia in the first place as a solvent, which does not attack the silica of the ore, and my process is based upon the volatility and selective solvent action of ammonia. In place of solutions'of caustic alkalis, solutions of alkaline earths, for example barium hydroxid or strontium hydroaid, may, be

For this purpose I employ am-' ployed, which compounds are hereinafter and in the claims included in the description alkali In order to carry the invention into ef- Q feet I introduce into a distilling apparatus a solution of caustic soda or other alkali of the desired degree of concentration, t0- gether with a suitable quantity of ammonia solution. The alkali solution used may for example contain 25 to 26 per cent. of caustic soda (NaOH) or an equivalent proportion of caustic potash (KOH) orot earth alkaline hydrate, but it may contain less. The ammonia solution used for the extraction may be of any concentration, but I prefer to use a solution containing about 200 grams of ammonia (NI-I per liter. On heating the distilling apparatus, ammonia and aqueous vapor are driven off and conducted throu h an overhead refrigerator, from whence the condensed ammoniacal liquor is distributed over the crushed or roasted ore contained in a closed filter. The ammoniacal liquor percolates through the ore and charged with the dissolved zinc oxid is allowed to drain back into the caustic soda solution contained in the distilling vessel, where "the zinc oxid is retained as zincate of soda, and the ammonia is again evaporated to repeat the cycle of operations without loss. The dissolved zinc oxid thus gradually accumulates in. the caustic soda liquor until the desired degree of concentration of zincate of soda is attained, the filter being replenished with zinc ore as it becomes eighausted. When the desired degree of concentration of the. zincate solution is attained, say when the solution .on analysis shows a content of grams ZnO per liter, the solution can he run OE and filtered. Constituents of zinc ore other than zinc oxid which may have been dissolved out by ammonia (such as hydrated oxide of iron, copper, or other metals) can be precipitated from the filtered solution by addition of a suficient quantity i of finely divided zinc metal and removed by filtration or decantation in order to be worked up further as desired.

By this process it is possible to treat even ores poor in zinc oxid with advantage, as the heat necessary to evaporate and clrculate the ammonia is small. If the ore containszinc carbonate it may be transformed into. oxid by addition of quick hme or barium hydroxid in the necessary proportions.-

The accompanying drawing represents diagrammatically an apparatus-for carrying out the invention.

a indicates a still into which the caustic or other alkali solution and the ammonia solution are introduced, and in which the dissolved zinc oxid extracted by the am monia from the ore in the vessel 1) gradually accumulates. The still a, is heated by an internal steam coil 0, and the ammonia driven off from the liquid in the still passes on by the pipe d to the coilof a condenser d where it is condensed and passes on by the pipe 0 to the vessel 6 in which it is distributed over the charge of zinc ore by the spraying head f. The ammonia solution of zinc oxid passes away from the vessel 6 to vthe still a by the pipes g, h, and the circulation through the apparatus continues until the zincate solution has attained the desired degree of concentration. The solution can then be run off by the cock 2'.

What I claim and desire to secure by Letters Patent is l. A continuous process of preparing concentrated solutions of alkali zincates from ores containing zinc oxid, comprising the following steps in repeated series; treating centrated solutions of zincate of soda from ores containing zinc oxid, comprising the following steps in repeated series; treating the ore with ammonia water, mixing the resulting solution with a solution of caustic soda and distilling off the ammonia and steam, and condensing the same to produce ammonia water, whereby the process is conducted as a continuous cycle, substantially. as specified.

In witness whereof, I have hereunto signed my name in the presence of two subscribing witnesses.

CHARLES RANSON.

Witnesses THOMAS LAING WHITEHEAD, FRANK RUssAK. 

